An experimental drug from the US-based Eli Lilly and Company discovered to protect Alzheimer's-inflicted mice from memory deterioration, despite a high-glycemic-index (GI) diet meant to boost blood sugar levels. The experimental drug mimics the hunger-signaling hormone ghrelin.
"With chronic diseases like diabetes and Alzheimer's, you need to do a long-term study," said examiner Inga Kadish, assistant professor at University of Alabama School of Medicine at Birmingham. "So we did an experiment with the worst-case scenario, a high-GI diet. Alzheimer's disease has 10 or 20 risk factors and some of the strongest risk factors are diabetes or metabolic syndrome."
"The present results suggest that ghrelin might improve cognition in Alzheimer's disease via a central nervous system mechanism involving insulin signaling," authors of the study printed in the journal Scientific Reports wrote.
In contrast to short-term administration of the ghrelin agonista drug -- which impairs insulin sensitivity and glucose tolerance, which are signs of metabolic syndrome and diabetes -- the researchers found that the long-term ghrelin agonist treatment did not impair insulin signaling and glucose tolerance in Alzheimer's disease mice fed with a high GI diet.
In the study, the Alzheimer's disease-model mice showed deterioration in spatial learning as they turned older -- in other words, they got lost when trying to swim to a platform hidden just beneath the water surface that they previously were trained to find in a four-foot-wide pool.
The test mice fed with the ghrelin agonist and the high-GI diet showed long-term cognitive enhancement in this water maze test as compared to the mice fed with a normal diet or high-GI diet only. The test mice also showed more activity, reduced body weight and fat mass. They also showed a beneficial impact of the long-term ghrelin agonist treatment on insulin signaling pathways in hippocampal brain tissue.
Alzheimer's patients show significant shrinkage of the hippocampus, a part of the brain cortex that has a key role in forming new memories.